How to rotate a circle around y axis in matlab?

Question

Ashkan Rigi 2022-4-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1708630-how-to-rotate-a-circle-around-y-axis-in-matlab

编辑： Image Analyst 2022-4-30

Hi every body. I have some circles with different radius (r) and I would like to rotate it around y axis. This is my code:

for r=1:10
    for teta=1:360
        r=1;    % radius
        C=[0 0];% center
        n=0.01;
        theta=0:n*pi/360:2*pi;   % the angle
        m=r*[cos(theta')+C(1) sin(theta')+C(2)]; % the points of circles
        R = [cosd(teta) -sind(teta); sind(teta) cosd(teta)]; % rotation matrix
        Ry = [cos(teta)  sin(teta); -sin(teta)  cos(teta)]
        point = m';
        Circlepointcloud = Ry*point;
        axis equal
        set(gca,'Visible','off')
        ax = gca;
        save_name = sprintf('Circlepointcloud_%02d_%03d',r,teta)
        save(save_name,'Circlepointcloud')
        Name=['Circle' sprintf('Circlepointcloud_%03d_%03d',r,teta) '.jpg'];
        exportgraphics(gca,Name,'Resolution',600);
        plot(Circlepointcloud(1,:),Circlepointcloud(2,:),'o','color','black')
    end
end

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Answer 1

Image Analyst 2022-4-30

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1708630-how-to-rotate-a-circle-around-y-axis-in-matlab#answer_954505

编辑：Image Analyst 2022-4-30

You need to add drawnow at the bottom of the loop so you can see the progress.

You also need to add the center of the circle to the equation and apply the rotation matrix to the CENTER of the circle, not the circle itself because obviously rotating a cirlce about its center will not show any difference. The center should not be at (0,0) or else you won't see any rotation of course.

See attached demos where I rotated an ellipse.